Light emitting device, method of manufacturing the same and monolithic light emitting diode array

ABSTRACT

A light emitting device including: at least one light emitting stack including first and second conductivity type semiconductor layers and an active layer disposed there between, the light emitting stack having first and second surfaces and side surfaces interposed between the first and second surfaces; first and second contacts formed on the first and second surface of the light emitting stack, respectively; a first insulating layer formed on the second surface and the side surfaces of the light emitting stack; a conductive layer connected to the second contact and extended along one of the side surfaces of the light emitting stack to have an extension portion adjacent to the first surface; and a substrate structure formed to surround the side surfaces and the second surface of the light emitting stack.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the priority of Korean Patent Application No.2007-27561 filed on Mar. 21, 2007, in the Korean Intellectual PropertyOffice, the disclosure of which is incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a light emitting device and amanufacturing method thereof, and more particularly, to a monolithiclight emitting diode array in which a circuit structure is easily formedto suit a variety of array configurations of a light emitting diode.

2. Description of the Related Art

In general, a semiconductor light emitting diode is beneficiallyapplicable as a light source in terms of output, efficiency orreliability. Thus, the semiconductor light emitting diode is vigorouslyresearched and developed as a high-output and high-efficiency lightsource capable of replacing a backlight of a lightening device or adisplay device.

In general, a light emitting diode is driven at a low direct current.Therefore, in order to drive the light emitting diode at a normalvoltage (direct current of 220V), an additional circuit, e.g.,alternating current/direct current (AC/DC) converter is required tosupply a low DC output voltage.

However, this additional circuit not only complicates configuration ofthe LED module but also potentially undermines efficiency andreliability. Also, such a complicated structure may cause errors in aprocess of mounting and assembling individual LEDs. In this case, theLED device may be ruined due to high inverse bias voltage.

To overcome this problem, there has been proposed an LED array which hascircuits connected to be driven in response to an alternating currentvoltage. However, these circuit connections are also complicated, thusposing difficulty to sufficient miniaturization of the LED array.

SUMMARY OF THE INVENTION

An aspect of the present invention provides a light emitting device inwhich a variety of circuit connection structures, particularly,complicated circuit connection structures can be easily formed to beoperable in response to an alternating current (AC) voltage, and amonolithic light emitting diode array.

An aspect of the present invention provides a method of manufacturing alight emitting device having a variety of circuit connection structures,particularly complicated circuit connection structures to be operable inresponse to the AC voltage, and a monolithic light emitting diode array.

According to an aspect of the present invention, there is provided a Alight emitting device including: at least one light emitting stackincluding first and second conductivity type semiconductor layers and anactive layer disposed therebetween, the light emitting stack havingfirst and second surfaces defined by the first and second conductivitytype semiconductor layers, respectively to oppose each other and sidesurfaces interposed between the first and second surfaces; a firstcontact formed on the first surface of the light emitting stack tocontact the first conductivity type semiconductor layer; a secondcontact formed on the second surface of the light emitting stack tocontact the second conductivity type semiconductor layer; a firstinsulating layer formed on the second surface excluding a portion wherethe second contact is formed and the side surfaces of the light emittingstack; a conductive layer connected to the second contact and extendedalong one of the side surfaces of the light emitting stack to have anextension portion adjacent to the first surface; and a substratestructure formed to surround the side surfaces and the second surface ofthe light emitting stack.

The substrate structure may be formed of a conductive material, thesubstrate structure further including a second insulating layer disposedbetween the light emitting stack and the substrate structure toelectrically insulate the second contact and the conductive layer of thelight emitting stack from the substrate structure. The substratestructure may be a metal layer formed by plating.

Alternatively, the substrate structure may be formed of an electricallyinsulating material. At this time, the second insulating layer may notbe required.

In the monolithic light emitting diode array, the at least lightemitting stack may include a plurality of light emitting stacks.

Portions of the conductive layers adjacent to the first surfaces may besubstantially flush with the first surfaces of the light emittingstacks, respectively. Portions of the conductive layers adjacent to thefirst surfaces may be lower than the first surfaces of the lightemitting stacks, respectively.

The light emitting device may include at least one circuit layer formedto electrically connect the light emitting stacks to one another. The atleast one circuit layer may include a circuit layer connecting anexposed portion of the conductive layer of one of the light emittingstacks to the first contact of another light emitting stack. The atleast one circuit layer may include a circuit layer connecting anexposed portion of the conductive layer of one of the light emittingstacks to an exposed portion of the conductive layer of another lightemitting stacks. The light emitting device may further include a thirdinsulating layer formed on a portion of the first surface of the lightemitting stack where the circuit layer is to be formed. The plurality oflight emitting stacks may be electrically connected to one another to beoperable in response to an alternating current voltage.

According to another aspect of the present invention, there is provideda method of manufacturing a light emitting device, the method including:forming at least one light emitting stack on a growth substrate toinclude first and second conductivity type semiconductor layers and anactive layer therebetween, wherein the light emitting stack has firstand second surfaces defined by the first and second conductivity typesemiconductor layers, respectively to oppose each other and sidesurfaces interposed therebetween; forming a second contact on at least aportion of the second surface of the light emitting stack and then afirst insulating layer on the second surface excluding the portion wherethe second contact is formed and the side surfaces of the light emittingstack; forming a conductive layer connected to the second contact andextended along one of the side surfaces of the light emitting stack to aportion adjacent to the first surface; forming a substrate structure tosurround the side surfaces and the second surface of the light emittingstack; separating the light emitting stack from the growth substrate toexpose the portion of the conductive layer extended to the firstsurface; and forming a first contact on the first surface of the lightemitting stack to contact the first conductivity type semiconductorlayer.

The substrate structure may be formed of a conductive material. Here,the method may further include forming a second insulating layer on theside surfaces and the second surface of the light emitting stack,between the forming a conductive layer and the forming a substratestructure.

The forming a substrate structure may be performed by plating.

The substrate structure may be formed of an electrically insulatingmaterial.

The forming a second contact and then a first insulating layer mayinclude: forming a first insulating layer on the second surfaceexcluding a portion where the second contact is to be formed and theside surface of the light emitting stack; and forming the second contacton the second surface where the first insulating layer is not formed.

The at least one light emitting stack may include a plurality of lightemitting stacks, and the forming at least one light emitting stackincludes: forming the first conductivity type semiconductor layer, theactive layer and the second conductivity type semiconductor layersequentially on the growth substrate; and mesa-etching the formed layersto obtain the plurality of light emitting stacks.

The first insulating layers may be extended to portions between theplurality of light emitting stacks, respectively, and wherein the methodmay include removing the portions of the first insulating layers formedbetween the plurality of light emitting stacks.

The mesa-etching may be performed to expose the growth substrate in theportions between the plurality of light emitting stacks. The forming aconductive layer may include forming the conductive layer connected tothe second contact and extended along one of the side surfaces of eachof the light emitting stacks to the exposed portions of the growthsubstrate.

The mesa-etching may be performed such that the first conductive layerat least partially remains in the portions between the plurality oflight emitting stacks. The forming a conductive layer may includeforming the conductive layer connected to the second contact andextended along one of the side surfaces of each of the light emittingstacks to the remaining first conductivity type nitride semiconductorlayer.

According to still another aspect of the present invention, there isprovided a monolithic light emitting diode array including: first tofifth light emitting diode cells each comprising a light emitting stackhaving first and second conductivity type semiconductor layers and anactive layer disposed therebetween, a first contact formed to contactthe first conductivity type semiconductor layer and a second contactlayer formed to contact the second conductivity type semiconductorlayer; a substrate structure having the first to fifth light emittingdiode cells embedded therein to expose a surface of the secondconductivity type semiconductor layer where the second contact isformed; an insulating layer formed on a surface of the light emittingstack of each of the light emitting diode cells, embedded in thesubstrate structure excluding a portion where the second contact layeris formed; a conductive layer formed to have a portion in contact withthe second contact of the each light emitting diode cell, the conductivelayer extended along the insulating layer to have an extension portionadjacent to the top surface of the substrate structure; and a circuitlayer formed on the top surface of the substrate structure to connectone of the first contact and the extension portion of the conductivelayer of one of the light emitting cells to one of the first contact andthe extension portion of the conductive layer of another light emittingdiode cell.

The circuit layer may be formed such that the first contact of the firstlight emitting diode cell and the second contact of the second lightemitting diode cell are connected to one power terminal, the secondcontact of the third light emitting diode cell and the first contact ofthe second light emitting diode cell are connected to another powerterminal, the first contact of the fifth light emitting diode cell andthe second contacts of the first and fourth light emitting diode cellshave a common point of contact, and the second contact of the fifthlight emitting diode cell and the first contact of the second and thirdlight emitting diode cells have a common point of contact.

In the specification, “a light emitting stack” refers to a structurehaving epitaxial layers stacked to constitute a light emitting diode. A“light emitting diode (LED) cell” refers to a light emitting stackhaving a contact structure. Moreover, a “monolithic light emitting diodearray” refers to a light emitting device having a plurality of lightemitting stacks or light emitting diode (LED) cells. Therefore, themonolithic light emitting diode array is used similarly to a “lightemitting device having a plurality of light emitting stacks.”

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other aspects, features and other advantages of thepresent invention will be more clearly understood from the followingdetailed description taken in conjunction with the accompanyingdrawings, in which:

FIG. 1 is a side cross-sectional view illustrating a light emittingdevice according to an exemplary embodiment of the invention;

FIG. 2 is a side cross-sectional view illustrating one circuit structureof a monolithic light emitting diode array as a light emitting deviceaccording to another example of the invention;

FIG. 3 is a side cross-sectional view illustrating another circuitstructure of a monolithic light emitting diode array as a light emittingdevice according to still another example of the invention;

FIGS. 4A to 4G are procedural cross-sectional views for explaining amethod of manufacturing a monolithic light emitting diode arrayaccording to an exemplary embodiment of the invention;

FIGS. 5A to 5G are a procedural view for explaining a method ofmanufacturing a monolithic light emitting diode array according toanother exemplary embodiment of the invention;

FIG. 6A is a view illustrating an arrangement of a monolithic lightemitting diode array according to an exemplary embodiment of theinvention and FIG. 6B is an equivalent circuit diagram of FIG. 6A; and

FIGS. 7A to 7C are side cross-sectional views illustrating a circuitstructure applicable to the monolithic light emitting diode array shownin FIG. 6A.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Exemplary embodiments of the present invention will now be described indetail with reference to the accompanying drawings.

FIG. 1 is a side cross-sectional view illustrating a light emittingdevice according to an exemplary embodiment of the invention. FIG. 1shows a light emitting device configured as a single cell structure inwhich a variety of circuit connections can be easily formed.

As shown in FIG. 1, the light emitting device 10 of the presentembodiment includes a light emitting stack 11 having first and secondconductivity-type semiconductor layers 11 a and 11 b and an active layer11 c disposed therebetween, and a substrate structure 17 formed tosurround a bottom surface and side surfaces of the light emitting stack11. The light emitting stack 10 applicable to the present embodiment maybe formed of not only AlGaInN but also a known semiconductor materialsuch as AlGaAs, AlGaInP, and ZnO.

First and second contacts 18 and 13 are formed on a top surface and thebottom surface of the light emitting stack 11 to contact the first andsecond conductive semiconductor layers 11 a and 11 b, respectively.Light generated from the active layer 11 c is emitted through the top ofthe light emitting stack 11, i.e., the first conductivity typesemiconductor layer 11 a. To ensure effective light emission, as in thepresent embodiment, the first contact 13 is formed only on a portion ofthe top surface of the light emitting stack 11. Alternatively, the firstcontact 13 may be formed of a light transmissive electrode material.

A first insulating layer 12 a is formed on a portion of the bottomsurface of the light emitting stack 11 where the second contact 13 isnot formed and side surfaces thereof. The first insulating layer 12 amay be a high resistance oxide or a nitride such as SiO₂, Si₃N₄, AlN,and Al₂O₃.

The light emitting device 10 include a conductive layer 14 connected tothe second contact 13 and extended along one of the side surfaces of thelight emitting stack 11. Here, the conductive layer 14 may beelectrically insulated from the light emitting stack 11 by the firstinsulating layer 12 a. A portion of the conductive layer 14 adjacent tothe top surface of the light emitting stack 11 is exposed toward the topsurface. An exposed portion of the conductive layer 14 and the firstcontact 18 (other conductive material areas extended from respectiveparts) may be provided as a bonding area connected to an externalcircuit.

According to the present embodiment, the substrate structure 17 may bemade of a conductive material. The conductive material is generally highin thermal conductivity and thus may be utilized as a substrate of thelight emitting device 10. The substrate structure 17 may be a metallayer and formed by plating to easily obtain a sufficient thickness as asupporting body. As described above, when the substrate structure 17 iselectrically conductive, a second insulating layer 12 b is additionallyformed between the light emitting stack 11 and the substrate structure17. The second insulating layer electrically insulates the secondcontact 13 and the conductive layer 14 of the light emitting stack 11from the substrate structure 17. Of course, the substrate structure 17may be made of an electrically insulating material. Here, the secondinsulating layer 12 b may not be required.

As described above, the second contact 13 embedded in the substratestructure 17 is led out to the top surface of the substrate structure 17through an electrode lead-out structure having the conductive layer 14and the first and second insulating layers 12 a and 12 b. This allowsthe contact areas of opposite polarity to be formed on a substantiallyidentical surface.

The plurality of light emitting stacks structured as above, when appliedto a monolithic light emitting diode array, easily allows a circuitstructure in which the light emitting stacks are connected in serieswith or parallel to one another.

FIGS. 2 and 3 are side cross-sectional views illustrating examples of acircuit structure of a monolithic light emitting device according toanother exemplary embodiment of the invention. The monolithic lightemitting diode arrays shown in FIGS. 2 and 3 are understood to be aserial and parallel structure, respectively.

First, FIG. 2 illustrates the monolithic light emitting diode array 20having two light emitting stacks 21 provided as respective LED cells 20Aand 20B connected in series with each other.

Each of the light emitting stacks 21 includes first and secondconductivity-type semiconductor layers 21 a and 21 b, and an activelayer 21 c disposed therebetween. Also, the light emitting diode array20 includes a substrate structure 27 surrounding a bottom surface andside surfaces of the light emitting stack 21.

First and second contacts 28 and 23 are formed on a top surface and thebottom surface of the light emitting stack 21 to contact the first andsecond conductivity type semiconductor layers 21 a and 21 b,respectively. The first contact 28 is formed only on a portion of thetop of the light emitting stack 21. Alternatively, to ensure light to beemitted more effectively, the first contact 28 may be formed of atransparent electrode material. Of course, as in the present embodiment,the first contact 28, even when formed only partially on the top surfaceof the light emitting stack 21, may be formed of a transparent electrodematerial. Moreover, to assure the light emitting stacks 21 to beconnected through circuits easily, the first contact 28, as shown, maybe formed at an edge of the top surface of the light emitting stack 21.

A first insulating layer 22 a is formed on a portion of the bottomsurface of the light emitting stack 21 where the second contact 23 isnot formed and side surfaces thereof. The first insulating layer 22 amay be made of a high-resistance oxide or a nitride such as SiO₂, Si₃N₄,AlN, and Al₂O₃.

Also, the light emitting device 20 includes a conductive layer 24connected to the second contact 23 and extended along one of the sidesurfaces of the light emitting stack 21. Here, the conductive layer 24may be electrically insulated from the light emitting stack 21 by thefirst insulating layer 22 a.

Here, the conductive layer 24 may be extended to an appropriate one ofthe side surfaces of the light emitting stack 21 according to a desiredcircuit connection structure of the LED cells. That is, as in thepresent embodiment, to ensure the LED cells to be connected in series,the conductive layer 24 of one 20B of the LED cells may be extendedalong the side surface adjacent to another LED cell 20A.

The conductive layer 24 is extended to a portion adjacent to the topsurface of the light emitting stack 21 so that the embedded secondcontact 23 can be connected to the conductive layer 24 connected toanother second contact 23 or the first contact 28 by an additionalcircuit layer 29.

That is, as in the present embodiment, the conductive layer 24 of theLED cell 20B is extended from the first contact 28 of the LED cell 20B,and can be connected to the first contact 28 of another adjacent LEDcell 20A by the circuit layer 29. FIG. 2 illustrates only the two LEDcells 20A and 20B. But it is easily apparent to those skilled in the artthat this connection structure can be applied in a similar fashion tothree LED cells or more.

In the present embodiment, the substrate structure 27 may be made of aconductive material. The substrate structure 27 may be a metal layerformed by plating. The substrate structure 27 is electricallyconductive, and thus a second insulating layer 22 b may be additionallyformed between the light emitting stack 21 and the substrate structure27. The second insulating layer 22 b electrically insulates the secondcontact 23 and the conductive layer 24 of the light emitting stack 21from the substrate structure 27.

To effectively prevent the circuit layer 29 from contacting an undesiredarea of the light emitting stack 21, a third insulating layer 22 c maybe additionally formed on the top surface of the light emitting stack 21where the circuit layer 29 is to be formed.

As described above, the second contact 23 embedded in the substratestructure 27 may be led out to the top surface of the substratestructure 27 through an electrode lead-out structure having theconductive layer 24 and the first and second insulating layers 22 a and22 b. This allows the first and second contacts 28 and 23 to be formedon a substantially identical surface. Therefore, the LED cells can beeasily connected in series together by the circuit layer 29 formed in asimple process.

The monolithic light emitting diode array 30 shown in FIG. 3 has acircuit structure of LED cells 30A and 30B connected in parallel witheach other.

As shown in FIG. 3, the monolithic light emitting diode array includestwo light emitting stacks 21 provided as respective LED cells 30A and30B. Each of the light emitting stacks 31 includes first and secondconductivity-type semiconductor layers 31 a and 31 b, and an activelayer 31 c disposed therebetween. The light emitting diode array 30 alsoincludes a substrate structure 37 surrounding a bottom surface and sidesurfaces of the light emitting stack 31.

In a similar manner to the previous embodiment, fist and second contacts38 and 33 are formed on a top surface and the bottom surface of thelight emitting stack 31 to contact the first and second conductivitytype semiconductor layers 31 a and 31 b, respectively. The first contact38 is formed only on a portion of the top surface of the light emittingstack 31.

A first insulating layer 32 a is formed on a portion of the bottomsurface of the light emitting stack 31 where the second contact 33 isnot formed and side surfaces thereof. The first insulating layer 32 amay be made of a high-resistance oxide or a nitride such as SiO₂, Si₃N₄,AlN, and Al₂O₃. Also, the light emitting device 30 includes a conductivelayer 34 connected to the second contact 33 and extended along one ofthe side surfaces of the light emitting stack 31. Here, the conductivelayer 34 may be electrically insulated from the light emitting stack 31by the first insulating layer 32 a.

In the present embodiment, the substrate structure 37 may be made of aconductive material. The substrate structure 37 may be a metal layerformed by plating. The substrate structure 37 is electricallyconductive, and thus a second insulating layer 32 b may be additionallyformed between the light emitting stack 31 and the substrate structure37. As described in the previous embodiment, the second insulating layer32 b electrically insulates the second contact 33 and the conductivelayer 34 of the light emitting stack 31 from the substrate structure 37.

Also, in the present embodiment, to allow the LED cells to be connectedin parallel to each other, the conductive layer 34 of one of the twoadjacent LED cells 30A and 30B may be extended along the side surfaceadjacent to another LED cell 30A or 30B. In this structure, therespective conductive layers 34 of the LED cells 30A and 30B may beconnected to each other. The conductive layers 34 of the LED cells 30Aand 30B, even though not connected directly to each other, may haverespective portions adjacent to the top surfaces of the correspondingLED cells connected together by a circuit layer 39. This allows theembedded second contacts 33 of the LED cells 30A and 30B to beelectrically connected together.

To effectively prevent the circuit layer 38 from contacting an undesiredarea of the light emitting stack 31, a third insulating layer 32 c maybe additionally formed on the top surface of the light emitting stack 31where the circuit layer 39 is to be formed.

FIG. 3 illustrates only the two LED cells 30A and 30B. But it is easilyapparent to those skilled in the art that this connection structure canbe applied in a similar fashion to three LED cells or more.

As described above, similarly to the previous embodiment, the secondcontact 33 embedded in the substrate structure 37 is led out to the topsurface of the substrate structure 37 through an electrode lead-outstructure having the conductive layer 34 and the first and secondinsulating layers 32 a and 32 b. This allows the contact areas ofopposite polarity to be formed on a substantially identical surface.Therefore, as in the present embodiment, the LED cells can be easilyconnected in parallel together by the circuit layer 39 formed in asimple process.

The aforesaid light emitting device, or the monolithic light emittingdiode array including the plurality of LED cells and the circuitstructure may be manufactured by a general method of manufacturing avertical light emitting diode which adopts a process of separating asubstrate.

FIGS. 4A to 4G are procedural cross-sectional views for explaining amethod of manufacturing a monolithic light emitting diode arrayaccording to an exemplary embodiment of the invention.

First, as shown in FIG. 4A, an n-type semiconductor layer 111 a, anactive layer 111 c and a p-type semiconductor layer 111 b aresequentially grown on a growth substrate 110 and then the layers formedare mesa-etched to produce a plurality of light emitting stacks 111.

The n-type and p-type semiconductor layers 111 a and 111 b and theactive layer 111 c may be made of not only AlGaInN but also a knownsemiconductor material such as AlGaAs, AlGaInP, and ZnO. In the presentembodiment, the mesa-etching is performed to a depth enabling the growthsubstrate 110 to be exposed, thereby completely separating the epitaxiallayers 111 a, 111 b, and 111 c into two light emitting stacks 111. Asdescribed above, each of the two light emitting stacks 111 is defined bythe n-type and p-type semiconductor layers 111 a and 111 b. The lightemitting stack 111 has first and second surfaces opposing each other andside surfaces disposed therebetween.

Then, as shown in FIG. 4B, a first insulating layer 112 a is formed onthe second surface of the light emitting stack 111 excluding a portionwhere a contact is to be formed and the side surfaces thereof.

To form the insulating layer 112 a, an insulator is deposited on anentire area of the second surface and the side surfaces of the lightemitting stack 111 and then a desired area for forming the contact isselectively removed. The first insulating layer 112 a may be made of ahigh-resistance oxide or a nitride such as SiO₂, Si₃N₄, AlN, and Al₂O₃.

In the present embodiment, the first insulating layer 112 a is extendedto a portion between the light emitting stacks 111. In this case, afterseparating the light emitting stack 111, the portion of the firstinsulating layer 112 a formed between the light emitting stacks 111 maybe removed. Alternatively, in this process, the portion of the firstinsulating layer 112 a between the light emitting stacks 111 may beadditionally removed to expose the conductive layer, which is necessaryalong with a process of separating the growth substrate 110.

Subsequently, as shown in FIG. 4C, a p-type contact layer 113 is formedon an exposed contact-forming portion of the second surface of the lightemitting stack 111. A conductive layer 114 is formed to connect to thep-type contact layer 113 and extended along one of the side surfaces ofthe light emitting stack 111 to a portion adjacent to the first surface.

The p-type contact layer 113 may be made of an electrode material whichforms an ohmic contact with the p-type semiconductor layer 111 b. Theconductive layer 114 is extended from a portion of the p-type contactlayer 113 along the side surface of the light emitting stack 111 wherethe first insulating layer 112 a is formed, and then to the portionadjacent to the first surface. As described above, the side surfacehaving the conductive layer 114 formed thereon may be adjacent toanother light emitting stack to be connected with each other. Eventhough the p-contact layer 113 is embedded in the substrate structure110 in a later process, the conductive layer 114 connected to the p-typecontact layer 113 may have a portion exposed toward the first surface ofthe light emitting stack 111. This allows the light emitting stack 111to be connected suitably via circuits to another light emitting stack.

Thereafter, as shown in FIG. 4D, a second insulating layer 112 b may beformed on the side surfaces and the second surface of the light emittingstack 111.

The second insulating layer 112 b electrically insulates a substratestructure (117 of FIG. 4E) to be formed in a later process from theconductive layer 114. Therefore, the second insulating layer 112 b isformed to enclose at least the conductive layer 114. Similarly to thefirst insulating layer 112 a, the second insulating layer 112 b may bemade of a high resistance oxide or a nitride such as SiO₂, Si₃N₄, AlN,and Al₂O₃. The second insulating layer 112 b is required when thesubstrate structure 117 is formed of a conductive material. Therefore,in a case where the substrate structure 117 is formed of an electricallyinsulating material, the second insulating layer 112 b may not beformed.

Next, as shown in FIG. 4E, the substrate structure 117 is formed tosurround the side surfaces and the second surface of the light emittingstack 111.

In the present embodiment, the substrate structure 117 is obtainable byforming a seed layer 116 on the second insulating layer 112 b tofacilitate plating and then performing plating. The substrate structure117 is made of a metal material formed by plating, but not limitedthereto. As described above, the substrate structure 117 may utilize aninsulating substrate in place of a conductive substrate made of e.g.,metal.

Afterwards, as shown in FIG. 4F, the light emitting stack 111 is removedfrom the growth substrate 110. Optionally, as in the present embodiment,a third insulating layer 112 c may be formed on a portion of the firstsurface of the light emitting stack 111.

After forming the substrate structure 117, the growth substrate 110 isremoved from the light emitting stack 111. The growth substrate 110 maybe removed by a known process such as mechanical polishing or chemicalmechanical polishing, chemical etching, particularly by laser lift-off.Through this process, the previously formed conductive layer 114 can bepartially exposed at the first surface of the light emitting stack 111.An exposed portion of the conductive layer 114 may serve as an externalconnection structure for the p-side contact layer 113 embedded.

Finally, as shown in FIG. 4G, an n-side contact layer 118 is formed onthe first surface of the light emitting stack 111 to connect to then-type semiconductor layer 111 a. Then, a circuit layer 119 is formed toconnect the LED cells 120A and 120B to each other.

This process is associated with an exposed surface defined by removingthe growth substrate 110. The exposed surface includes the first surfaceof the light emitting stack 111. The desired n-side contact layer 118 isformed on a portion of the first surface of the light emitting stack111. The n-side contact layer 118 may be made of an electrode materialwhich forms an ohmic contact with the n-type semiconductor layer 111 b.Then, the circuit layer 119 is formed to connect the LED cells 120A and120B including the respective light emitting stacks 111 to each other.

As in the present embodiment, optionally, the process of forming thethird insulating layer 112 c on the first surface of the light emittingstack 111 may be additionally performed prior to the process of formingthe circuit layer 119. This process is aimed at preventing an undesiredconnection. In the monolithic light diode array 120 of the presentembodiment, similarly to FIG. 2, the circuit layer 119 connects then-side contact layer 118 of the LED cell 120A to the p-side contactlayer 113 of the LED cell 120B, i.e., the exposed portion of theconductive layer 114 connected to the p-side contact layer 113. However,as shown in FIG. 3, the monolithic light emitting diode array 120 mayeasily adopt other connection structures.

In the aforesaid manufacturing process, the epitaxial layers arecompletely separated by deep-mesa etching to expose a growth substratefor forming the light emitting stacks. However, alternatively, themesa-etching may be performed to produce the light emitting stacks,while partially leaving the expitaxial layers. Here, the conductivelayer is prevented from being impaired by a process such as laser liftoff.

FIGS. 5A to 5G are procedural cross-sectional views illustrating amethod of manufacturing a monolithic light emitting diode array usingshallow mesa etching according to an another exemplary embodiment of theinvention.

First, as shown in FIG. 5A, an n-type semiconductor layer 121 a, anactive layer 131 c and a p-type semiconductor layer 131 b aresequentially grown on a growth substrate 130 and then the layers formedare mesa-etched to produce a plurality of light emitting stacks 131.

In the process of separating the epitaxial layers into the plurality oflight emitting stacks 131 according to the present embodiment, theepitaxial layers 131 a, 131 b, and 131 c are mesa-etched to partiallyremain with a predetermined thickness t, particularly 131 a. Asdescribed above, the remaining portion has a thickness such that theconductive layer is prevented from being impaired during a process ofremoving the growth substrate and the remaining portion is easilyremoved in a later process.

In a similar manner to the light emitting stacks 111 shown in FIG. 4A,each of the two light emitting stacks 131 obtained through the aboveprocess is defined by the n-type and p-type semiconductor layers 131 aand 111 b. The light emitting stack 131 is structured to have first andsecond surfaces opposing each other and side surfaces disposedtherebetween.

Then, as shown in FIG. 5B, a first contact layer 132 a is formed on thesecond surface of the light emitting stack 131 excluding a portion wherea contact is to be formed and the side surfaces thereof.

To form the insulating layer 132 a, an insulator is deposited on anentire area of the second surface and the side surfaces of the lightemitting stack 131 and then a desired area for forming a contact isselectively removed. The first insulating layer 132 a may be made of ahigh-resistance oxide or a nitride such as SiO₂, Si₃N₄, AlN, and Al₂O₃.

Subsequently, as shown in FIG. 5C, a p-type contact layer 133 is formedon an exposed contact-forming portion of the second surface of the lightemitting stack 131. A conductive layer 134 is formed to connect to thep-type contact layer 133 and extended along one of the side surfaces ofthe light emitting stack 131 to a portion adjacent to the first surface.

The p-type contact layer 133 may be made of an electrode material whichforms an ohmic contact with the p-type semiconductor layer 131 b. Theconductive layer 134 is extended from a portion of the p-side contactlayer 133 along the side surface of the light emitting stack 131 wherethe first insulating layer 132 a is formed, and then to the portionadjacent to the first surface.

Even though the p-side contact layer 133 is embedded in the substratestructure 130 in a later process, the conductive layer 134 connected tothe p-side contact layer 133 may have a portion exposed toward the firstsurface of the light emitting stack 131. This allows the light emittingstack 131 to be connected suitably via circuits to another lightemitting stack.

Thereafter, as shown in FIG. 5D, a second insulating layer 132 b may beformed on the side surfaces and the second surface of the light emittingstack 131.

The second insulating layer 132 b electrically insulates a substratestructure (137 of FIG. 5E) to be formed in a later process from theconductive layer 134. Therefore, the second insulating layer 132 b isformed to enclose at least the conductive layer 134.

Next, as shown in FIG. 5E, the substrate structure 137 is formed tosurround the sides and the second surface of the light emitting stack131.

In the present embodiment, the substrate structure 137 is obtainable byforming a seed layer 136 on the second insulating layer 132 b tofacilitate plating and then performing plating. The substrate structure137 is made of a metal material formed by plating, but not limitedthereto. The substrate structure 137 may utilize an insulating substratein place of a conductive substrate made of e.g., metal.

Afterwards, as shown in FIG. 5F, the light emitting stack 131 is removedfrom the growth substrate 130. Optionally, as in the present embodiment,a third insulating layer 132 c may be formed on a portion of the firstsurface of the light emitting stack 131.

After forming the substrate structure 137, the growth substrate 130 isremoved from the light emitting stack 131. The growth substrate 130 maybe removed by a known process such as mechanical polishing or chemicalmechanical polishing, particularly by laser lift off.

The conductive layer 134 is protected by a remaining epitaxial layerportion S and thus prevented from being damaged by chemical mechanicalpolishing or laser lift-off in the removal process of the growthsubstrate. Also, the remaining epitaxal layer portion S needs to beremoved together with a portion of the first insulating layer topartially expose the conductive layer 134. The remaining epitaxial layerportion may be removed by laser radiation. However, optionally,additional etching may be performed to partially expose the conductivelayer 134, which is a necessary process for circuit connections.

The previously formed conductive layer 134 can be partially exposed atthe first surface of the light emitting stack 131. An exposed portion ofthe conductive layer 134 may serve as an external connection structurefor the p-side contact layer 133 embedded.

Finally, as shown in FIG. 5G, an n-side contact layer 138 is formed onthe first surface of the light emitting stack 131 to connect to then-type semiconductor layer 131 a. Then, a circuit layer 139 is formed toconnect the LED cells 140A, and 140B to each other.

In this process, the growth substrate 130 is removed to define anexposed surface. The exposed surface includes the first surface of thelight emitting stack 131. The desired n-side contact layer 138 is formedon a portion of the first surface of the light emitting stack 131. Then-side contact layer 138 may be made of an electrode material whichforms an ohmic contact with the n-type semiconductor layer 131 b.

Then, the circuit layer 139 is formed to connect the LED cells 140A and140B including the respective light emitting stacks 131 to each other.

As in the present embodiment, optionally, the process of forming thethird insulating layer 132 c on the first surface of the light emittingstack 131 may be additionally formed prior to the process of forming thecircuit layer 139. This process is aimed at preventing the circuit layer139 form contacting an undesired area. In the monolithic light emittingdiode array 140 of the present embodiment, similarly to FIG. 2, thecircuit layer 139 connects the n-side contact layer 133 of the LED cell140A to the p-side contact layer 133 of the LED cell 140B i.e., theexposed portion of the conductive layer 139 connected to the p-sidecontact layer 133. However, as shown in FIG. 3, the monolithic lightemitting diode array 130 may easily adopt other connection structures.

The monolithic light emitting diode array of the present embodiment hasan external connection structure of the both contacts formed on thesubstantially identical surface. This allows easy complicated connectionof the plurality of LED cells to one another via circuits. Especially,the monolithic light emitting device connected to be operable inresponse to an alternating current voltage tends to require complicatedcircuit structures. Therefore, the monolithic light emitting device ofthe present invention is beneficially applicable.

FIG. 6A is a layout diagram illustrating a monolithic light emittingdiode array according to an exemplary embodiment of the invention. FIG.6B illustrates an equivalent circuit of the monolithic light emittingdiode array.

The monolithic light emitting diode array shown in the layout diagram ofFIG. 6A includes first and second LED cells A1 and A2 formed at one edgeand third and fourth LED cells C1 and C2 formed at an opposing edge, andthree five LED cells B1, B2, and B3 disposed between the first andsecond LED cells A1 and A2 and the third and fourth LED cells C1 and C2.

Hereinafter, referring to FIG. 6B, a circuit structure of the monolithiclight emitting diode array will be described.

First, an n-side contact of the first LED cell A1 and a p-side contactof the second LED cell A2 are connected to a first alternating current(AC) power terminal P1. A p-side contact of the third LED cell C1 andthe n-side contact of the second LED cell C2 are connected to a secondAC power terminal P2.

The three fifth LED cells B1, B2, and B3 are connected to one another inseries. An n-contact of the fifth LED cell B1 disposed at one peripheralside of the array, i.e., between the first and fourth LED cells A1 andC2 forms a common point of contact with respective p-side contacts ofthe first and fourth LED cells A1, and C2. A p-side contact of the fifthLED cell B3 disposed at another peripheral side of the array between thesecond and third LED cells A2 and C1 forms a common point of contactwith respective n-side contacts of the second and third LED cells A2,and C1.

In the light emitting diode array according to the above layout, thethree fifth LED cells B1, B2, and B3 are always driven until the ACvoltage is applied to the power terminals P1, and P2. Also, the firstand fourth LED cells A1 and C2 and the second and third LED cells A2 andC1 may be driven alternatively according to a cycle of the AC voltage.As a result, even with the AC voltage applied, the five LED cells B1,B2, and B3 can be driven successively.

Moreover, the layout of the monolithic light emitting diode array isadvantageous in terms of a breakdown voltage. The voltages applied tothe LED cells may be substantially similar to one another in view ofresistance of the breakdown voltage. This design is effectively achievedby disposing the LED cells to occupy a substantially identical area. Inaddition, to this end, the number of fifth LED cells can be properlyadjusted. The number of the fifth LED cells may range from 1 to 4.

As shown in FIG. 6A, the AC monolithic light emitting diode array hascomplicated circuit structure, posing a difficulty to configuration.However, such a circuit structure can be easily realized according tothe present embodiment.

The monolithic light emitting diode shown in FIG. 6A can be configuredin circuit structures shown in FIGS. 7A to 7C.

FIGS. 7A to 7C are side cross-sectional views illustrating themonolithic light emitting diode array of FIG. 6A cut along the lineX1-X1′, X2-X2′ and Y-Y′, respectively, according to an exemplaryembodiment of the invention. FIGS. 7A to 7C may be explained withreference to FIGS. 2 and 3. Here, in the present embodiment,mesa-etching for forming light emitting stacks and structures thereofare illustrated in a similar manner to FIG. 3.

FIGS. 7A to 7C illustrate a substrate structure 157 having the three LEDcells corresponding to respective trimming directions embedded therein.Each of the LED cells includes a light emitting stack 151 having n-typeand p-type semiconductor layers 151 a, and 151 b and an active layer 151c disposed therebetween. The LED cells include the substrate structure157 formed to surround a bottom surface and side surfaces of the lightemitting stack 151.

Even though not partially shown depending on the trimming direction, n-and p-side contracts 158 and 153 are formed on a top surface and thebottom surface of the light emitting stack 151. A first insulating layer152 a is formed on a portion of the bottom of the light emitting stack151 where the p-side contact 153 is not formed and the side surfacesthereof.

A conductive layer 154 is formed to connect to the p-side contact 153and extended along one of the side surfaces of the light emitting stack151. The conductive layer 154 may be insulated from the light emittingstack 151 by the first insulating layer 152 a.

Circuit connections of the contacts shown in FIG. 6A will be describedwith reference to FIGS. 7A to 7C.

First, referring to FIG. 7A, the conductive layers 154 of the LED cellsA1, and C2 are extended to the respective side surfaces adjacent toanother LED cell or a type of contact to which the respective p-sidecontacts are to be connected. That is, in the structure of FIG. 7A,(X1-X1′ of FIG. 6A), the conductive layers 154 of the first and fourthLED cells A1 and C2 may be extended to the respective side surfacesadjacent to the fifth LED cell B1.

To connect the light emitting stacks via circuits, the conductive layer154 has an exposed portion adjacent to the top surface of the lightemitting stack 151. The exposed portions of the first and fourth LEDcells A1, and C2 are electrically connected to an n-side contact 158 ofthe fifth LED cell B1 by the circuit layer 159. This allows the p-sidecontacts 153 of the first and fourth LED cells A1, and C2 to have acommon point of contact with the n-side contact 158 of the fifth LEDcell B1.

Referring to FIG. 7B, which is cut along the line X2-X2′ of FIG. 6A, aconductive layer 154 of the fifth LED cell B3 disposed between thesecond and third LED cells A2, and C1 is extended along the two sidesurfaces adjacent to the second and third LED cells A2, and C1,respectively. To connect the light emitting stacks via circuits, theconductive layer 154 has exposed portions adjacent to the top surface ofthe light emitting stack 151.

The exposed portions of the conductive layer 154 of the fifth LED cellB3 are electrically connected to respective n-side contacts 158 of thesecond and third LED cells A2 and C1 by the circuit layer 159. Thisallows the n-side contacts 158 of the second and third LED cells A2, andC1 to have a common point of contact with the p-side contact 153 of thefifth LED cell B3 disposed therebetween.

Referring to FIG. 7C, which is cut along the line Y-Y′, the three fifthLED cells B1, B2, and B3 are connected in series with one another. Theconductive layers 154 of the fifth LED cells B1 and B2 are extended torespective side surfaces adjacent to other fifth LED cells B2 and B3. Toconnect the LED cells via circuits, the conductive layers 154 haverespective exposed portions adjacent to the top surface of the lightemitting stack 151.

The exposed portions of the conductive layers 154 of the fifth LED cellsB1 and B2 are electrically connected to n-side contacts 158 of the otherfifth LED cells B2 and B3 by the circuit layer 159. This allows thethree fifth LED cells B1, B2, and B3 to be connected in parallel to oneanother.

As described above, the LED cells can be easily connected to one anotheraccording to location of the conductive layers 154 for leading out thep-side contact 153 embedded in the substrate structure 157 and thecircuit layer 159. Especially, even though described separatelydepending on the trimming direction, each corresponding component isformed by an identical process, and the monolithic light emitting diodearray having a complicated circuit structure shown in FIG. 6A can bemore effectively manufactured.

Even though not described in the aforesaid embodiment, a thirdinsulating layer 158 may be additionally formed corresponding tolocation of the circuit layer 159. The third insulating layer 153prevents the light emitting stack 151 from contacting an externalcomponent such as the circuit layer, thereby protecting the lightemitting stack 151.

As set forth above, according to exemplary embodiments of the invention,one contact embedded in a substrate structure is led out through aconductive layer thereby to form both contacts on a substantiallyidentical surface. This light emitting device may be applied to aplurality of LED cells configured as a monolithic structure. This allowsan LED array with complicated connections, such as serial, parallelconnection or combination thereof to be easily produced using a circuitlayer formed coplanarly.

While the present invention has been shown and described in connectionwith the exemplary embodiments, it will be apparent to those skilled inthe art that modifications and variations can be made without departingfrom the spirit and scope of the invention as defined by the appendedclaims.

1. A light emitting device comprising: at least one light emitting stackincluding first and second conductivity type semiconductor layers and anactive layer disposed therebetween, the light emitting stack havingfirst and second surfaces defined by the first and second conductivitytype semiconductor layers, respectively to oppose each other and sidesurfaces interposed between the first and second surfaces; a firstcontact formed on the first surface of the light emitting stack tocontact the first conductivity type semiconductor layer; a secondcontact formed on the second surface of the light emitting stack tocontact the second conductivity type semiconductor layer; a firstinsulating layer formed on the second surface excluding a portion wherethe second contact is formed and the side surfaces of the light emittingstack; a conductive layer connected to the second contact and extendedalong one of the side surfaces of the light emitting stack to have anextension portion adjacent to the first surface; and a substratestructure formed to surround the side surfaces and the second surface ofthe light emitting stack.
 2. The light emitting device of claim 1,wherein the substrate structure is formed of a conductive material, thesubstrate structure further comprising a second insulating layerdisposed between the light emitting stack and the substrate structure toelectrically insulate the second contact and the conductive layer of thelight emitting stack from the substrate structure.
 3. The light emittingdevice of claim 2, wherein the substrate structure comprises a metallayer formed by plating.
 4. The light emitting device of claim 1,wherein the substrate structure is formed of an electrically insulatingmaterial.
 5. The light emitting device of claim 1, wherein the at leastlight emitting stack comprises a plurality of light emitting stacks. 6.The light emitting device of claim 5, wherein portions of the conductivelayers adjacent to the first surfaces are substantially flush with thefirst surfaces of the light emitting stacks, respectively.
 7. The lightemitting device of claim 5, wherein portions of the conductive layersadjacent to the first surfaces are lower than the first surfaces of thelight emitting stacks, respectively.
 8. The light emitting device ofclaim 5, comprising at least one circuit layer formed to electricallyconnect the light emitting stacks to one another.
 9. The light emittingdevice of claim 8, wherein the at least one circuit layer comprises acircuit layer connecting an exposed portion of the conductive layer ofone of the light emitting stacks to the first contact of another lightemitting stack.
 10. The light emitting device of claim 8, wherein the atleast one circuit layer comprises a circuit layer connecting an exposedportion of the conductive layer of one of the light emitting stacks toan exposed portion of the conductive layer of another light emittingstacks.
 11. The light emitting device of claim 8, further comprising athird insulating layer formed on a portion of the first surface of thelight emitting stack where the circuit layer is to be formed.
 12. Thelight emitting device of claim 8, wherein the plurality of lightemitting stacks are electrically connected to one another to be operablein response to an alternating current voltage. 13-28. (canceled)
 29. Amonolithic light emitting diode array comprising: first to fifth lightemitting diode cells each comprising a light emitting stack having firstand second conductivity type semiconductor layers and an active layerdisposed therebetween, a first contact formed to contact the firstconductivity type semiconductor layer and a second contact layer formedto contact the second conductivity type semiconductor layer; a substratestructure having the first to fifth light emitting diode cells embeddedtherein to expose a surface of the second conductivity typesemiconductor layer where the second contact is formed; an insulatinglayer formed on a surface of the light emitting stack of each of thelight emitting diode cells, embedded in the substrate structureexcluding a portion where the second contact layer is formed; aconductive layer formed to have a portion in contact with the secondcontact of the each light emitting diode cell, the conductive layerextended along the insulating layer to have an extension portionadjacent to the top surface of the substrate structure; and a circuitlayer formed on the top surface of the substrate structure to connectone of the first contact and the extension portion of the conductivelayer of one of the light emitting cells to one of the first contact andthe extension portion of the conductive layer of another light emittingdiode cell.
 30. The monolithic light emitting diode array of claim 29,wherein the circuit layer is formed such that the first to fifth lightemitting cells are electrically connected to one another to be operablein response to an alternating current voltage.
 31. The monolithic lightemitting diode array of claim 30, wherein the circuit layer is formedsuch that the first contact of the first light emitting diode cell andthe second contact of the second light emitting diode cell are connectedto one power terminal, the second contact of the third light emittingdiode cell and the first contact of the second light emitting diode cellare connected to another power terminal, the first contact of the fifthlight emitting diode cell and the second contacts of the first andfourth light emitting diode cells have a common point of contact, andthe second contact of the fifth light emitting diode cell and the firstcontact of the second and third light emitting diode cells have a commonpoint of contact.
 32. The monolithic light emitting diode array of claim31, wherein the fifth light emitting diode cell comprises a plurality oflight emitting diode cells connected in a serial configuration, whereina first contact of a light emitting diode cell located at one end in theserial configuration has a common point of contact with the secondcontacts of the first and fourth light emitting diode cells and a secondcontact of a light emitting diode cell located at another end in theserial configuration has a common point of contact with the firstcontacts of the second and third light emitting diode cells.
 33. Themonolithic light emitting diode array of claim 32, wherein the fifthlight emitting diode cell comprises two to four light emitting diodecells.